This invention relates to electromagnetic contactors. In particular, it is an improved electromagnetic contactor that is adapted for use with one, two, three or four poles.
An electrical contactor is a switch that is designed to open and close repeatedly to supply and interrupt electricity at power levels to electrical loads such as motors and the like. An electromagnetic contactor is a contactor that is caused to operate by an electromagnet. The contactor is distinguished from a relay, which typically opens and closes electrical circuits to apply and remove control signals at relatively low currents. Contactors are also distinguished from circuit breakers in that a circuit breaker is a protective device, normally operated manually or by a motor or the like, that is designed for relatively infrequent operation to open in case of an overload. Thus, a complete installation that supplies power to an electrical load will normally include a circuit breaker in series with a contactor. The circuit breaker will trip and open on an overload and thus protect both the contactor and the load from damage, while normal operation that applies power to and removes it from the load is handled by the contactor. A contactor is typically designed to operate for as many as ten million cycles, while a circuit breaker is typically designed for thousands or tens of thousands of cycles.
One example of the state of the art and electromagnetic switches is given in U.S. Pat. No. 3,643,187 entitled "Electromagnetically Operated Switch Construction." The patent No. '187 teaches contacts that are bought into engagement by energizing an electromagnet and that are separated by the force of a spring when current is interrupted to the electromagnet. The apparatus that is taught by the patent No. '187 is assembled by screws and rivets, which complicate the manufacturing process, particularly if automatic assembly or assembly by robots is contemplated.
Another example of the state of the art is given in U.S. Pat. No. 3,235,686, entitled "Magnetic Switch With Readily Removable Electromagnetic Contact Unit." The apparatus taught in the patent No. '686 is designed to make it easy to reach the contacts for service without disconnecting the power wires to the contactor. This feature represents an advantage in operations, but the device as taught in the patent No. '686 is also assembled by screws and would be difficult to assemble automatically.
U.S. Pat. No. 3,179,771, entitled "Contactor With Reciprocating Armature and Novel Resilient Clip," teaches an exposed external electromagnet and return spring. The structure taught in the patent No. '771 is assembled by screws and rivets and would be extremely difficult to adapt to automatic assembly. U.S. Pat. No. 4,525,694, entitled "Electromagnet Contactor," features a three-pole contactor that is assembled without the use of screws or rivets. However, the apparatus taught in the patent No. '694 has a separate mounting and supporting frame that is snapped to the housing of the contactor to enable it to be mounted. The patent No. '694 also teaches contacts that are held in place by a spring snap. It appears that terminal screws in the patent No. '694 do not provide protection against loosening of the contact.